A follow-up study of 33 people who received Moderna Inc.’s Covid-19 vaccine in early trials show the antibodies it induced are still present six months after the second dose.

The U.S. government hit the accelerator on shipments of Covid-19 vaccines after a month of largely stagnant weekly deliveries, giving states the doses they say they need to finish vaccinating priority groups and open shots to all adults in the coming weeks.

One dose of Pfizer COVID-19 vaccine offers an immune response similar to that generated by infection and could also offer protection from variants to people who have previously had the virus, a British study said on March 26.

The United States administered 121,441,497 doses of COVID-19 vaccines in the country as of the morning of March 20 and distributed 156,734,555 doses, the U.S. Centers for Disease Control and Prevention said.

BioNTech SE could have capacity to make 3 billion doses of the Covid-19 vaccine the company developed with partner Pfizer Inc. during 2022, Bloomberg News reported on March 9, citing an interview with the German company’s chief executive officer.

The United States had administered 87,912,323 doses of Covid-19 vaccines as of early March 6 and delivered 116,355,405 doses, the Centers for Disease Control and Prevention said.

U.S. scientists are skeptical of a one-shot regimen for Pfizer Inc. and Moderna Inc. Covid-19 vaccines, saying there is not enough evidence that a single dose provides long-term protection, the Wall Street Journal reported.

Countries seeking their own COVID-19 vaccine doses are making deals with drug companies that threaten the supply for the global COVAX program for poor and middle-income countries, the World Health Organization said on Feb. 26.

Covid-19 vaccine makers told Congress on Feb. 23 that U.S. supplies should surge in the coming weeks due to manufacturing expansions and new vaccine authorizations.

Johnson & Johnson expects to be able to ship nearly 4 million doses of the company’s Covid-19 vaccine upon authorization in the U.S., an executive said at a hearing in the U.S. House of Representatives on Feb. 23.